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<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <style>
      body {
        margin: 0;
        padding: 0;
        background-image: url(../images/grid.png);
      }
      canvas {
        background-color: rgba(255, 0, 0, 0.1);
      }
    </style>
  </head>
  <body>
    <canvas id="tutorial" width="300" height="300">
      您的浏览器不兼容 Canvas，请升级您的浏览器。
    </canvas>

    <script>
      window.onload = function () {
        const canvasEl = document.getElementById('tutorial')
        if (!canvasEl.getContext) return
        const ctx = canvasEl.getContext('2d')

        ctx.save()
        ctx.translate(100, 100)
        ctx.fillRect(0, 0, 100, 50)
        ctx.restore()

        ctx.save()
        ctx.translate(150, 150)
        ctx.fillStyle = 'red'
        ctx.fillRect(0, 0, 50, 30)
        ctx.restore()
      }
    </script>
  </body>
</html>
